Various conveyance and processing devices are commonly used to transport and process blanks or stock material from a feed conveyor, through an assembly line or process. For example, in the production of packaging, webs of cardboard, paperboard, or corrugated material are moved through a rotary press or die drum to convert the web into individual blanks or sheets. In other instances, individual blanks or sheets move through various processing stations to have different functions performed on them, such as printing, cutting, etc. Individual sheets may be transferred from a die drum to a conveyor.
In traditional systems, to maintain control of the sheets during transfer from a die drum to a conveyor, the sheets are transferred from a nip point of the die drum to a nip point of the conveyor, e.g., a takeaway conveyor, and the distance between these nip points is static. However, it may be desirable to process sheets of varying length. Therefore, sheets that are longer than the distance between the nip point on the die drum and the nip point on the conveyor can be nipped by both the die drum and the conveyor at the same time. Such nipping of an individual sheet in two areas along its length simultaneously is undesirable. For example, if the speed of the die drum differs from that of the takeaway conveyor, portions of the sheets may be subjected to forces that result in damage to the sheets (e.g., skewing, marking, tearing). These forces, which may result in the slippage of a nip point over the material being transported and processed, can cause other damage as well, such as smearing of or damage to printing.
In one traditional system, the takeaway conveyor has been designed to include three support rollers at the end of the conveyor proximate the die drum. The conveyor belt is alternatingly wound around the three support rollers in a “S”-like manner. At least two of the support rollers are designed to be moveable such that the location of the nip point of the takeaway conveyor can be changed, and thus, the distance between the nip point on the die drum and the nip point on the conveyor can be changed. However, such configuration leaves at least one of the support rollers exposed outside the conveyor belt and accessible by incoming sheets. Accordingly, as a sheet approaches the front edge of the takeaway conveyor, it can be undesirably deflected toward and/or into the exposed roller, causing damage to the sheet and/or requiring stoppage of the conveyor for correction. In order to curb such undesirable deflection, this traditional system includes a relatively small deflector plate, typically comprised of metal, that extends across at least a portion of the area in which the exposed support roller is positioned. However, this deflector plate does not extend across very much of the front edge of the takeaway conveyor and thus does not entirely cover the area in which the exposed support roller is positioned. As such, there still exists the potential for undesirable deflection of the sheets toward and/or into the exposed roller, causing damage to the sheet and/or requiring stoppage of the conveyor for correction. Furthermore, having a deflector plate causes friction between the plate and the sheets, and can damage the sheets and any ink or markings on them. In a different device, a series of small rollers positioned on a shaft has been positioned on the intake end of a stacker, where the longitudinal position of the shaft can be adjusted. However, this configuration allows for minimal control over the sheets, and it is not able to deflect sheets under the rollers.
Accordingly, there is a need in the art for an apparatus and method that allows for adjustment of the distance between the nip points of adjacent processing apparatuses.